Switched-capacitor power supplies are commonly used in hearing aids and headsets, where efficiency and small sizes are important design parameters. The efficiency of a switched capacitor power supply has a maximum value when operating at a fixed input to output ratio. Traditionally, the way to optimize the efficiency is to design the circuitry supplied from the power supply to work at the input voltage times a fixed ratio, e.g. 2:1. In a hearing instrument, the input voltage is highly varying as it is a function of the battery voltage and the current being drawn from the battery. Supplying a fixed voltage from the switched-capacitor power supply at all times is therefore not optimal.